Rapid diffusion of wireless devices typified by mobile phones has promoted the use of switching devices. For example, high-frequency switches have been used in mobile terminals for high frequency communication to select high-frequency signals. Examples of the switch include mechanical switches and switches using a semiconductor transistor, for example.
Japanese Patent Application Publication No. 2006-109084 (Patent Document 1) and U.S. Pat. No. 7,848,712 (Patent Document 2) disclose providing an inductor between input/output terminals of a switch to improve isolation characteristics between the input/output terminals.
The technologies disclosed in Patent Documents 1 and 2 can cancel out the parasitic capacitance between the input/output terminals by the reactance component of the inductor, and thereby can improve the isolation characteristics. However, the parasitic capacitance value between the input/output terminals is small. Hence the effort to improve the isolation characteristics leads to the increase in the inductance of the inductor. Therefore, the above-described technologies are not practical.